president obama will travel to boston to attend a service for victims thursday. stay with wjz on air and online for complete coverage of the explosions at the boston marathon. for developments any time, log onto cbsbaltimore.com. and coming up at 7:00 p.m., scott pelley and the cbs evening news, live from boston. tune in for the latest on the investigation and the victims coming up, right here on eyewitness news. >>> wjz wants to update you on the breaking news we told you about a short time ago. cbs news now is confirming a letter sent to a u.s. senator's office preliminarily tests positive for the poison ricin. the letter was sent to republican senator roger wicker of mississippi. it was apparently an envelope. and the poison was detected at the u.s. capitol off-site mail facility in d.c. further testing on that envelope is under way right now. and senators are being briefed also right now on that situation. >>> well, today marks the 6th anniversary of another horrible act of violence. the massacre at virginia tech. people are remembering the victims murdered a